1. Field of the Invention
The invention lies in the field of internal combustion engines. The invention relates to a method of determining an operating parameter for starting an internal combustion engine, in particular, for determining the mass of fuel to be injected.
An internal combustion engine can be started without any special regulation if the starting operation is carried out with the aid of a starting function. The starting function uses the operating parameters as a basis to calculate one or more parameters for the injection system, with which parameters the internal combustion engine is then started. The operating parameters include, for example, the coolant temperature and the rotational speed from a number of characteristic maps. A change is made to speed regulation once a specific idling speed has been reached. DifficuLties arise from the fact that the same starting behavior is intended to be achieved with very different operating parameters.
A starting operation using a predefined starting function is illustrated in FIG. 3. In accordance with the predefined starting function, between time t1 and time t2, a mass m of fuel is injected as soon as the rotational speed of the internal combustion engine has reached the speed N.sub.ST using the starter. From time t2, the speed regulator takes over the regulation of the internal combustion engine. The predefined starting function, however, leads to severe overrunning of the speed N during the starting operation until the idling speed N_SP is finally reached. In order to avoid overrunning and to obtain reproducibility of the starting operations when the starting function is being predefined, it is necessary for all cross-influences in the starting function to be taken into account because the function involves open-loop control.
A computer-controlled injection system for diesel engines is disclosed in German Patent No. 30 09 627 C2. The injection system controls the starting valves at the beginning of the starting operation, and the triggering angle for the injection operation is calculated based on the crankshaft angle using a special program.